Semiconductor devices

ABSTRACT

A semiconductor device includes an active region on a substrate extending in a first direction, the active region having an upper surface and sidewalls, a plurality of channel layers above the active region to be vertically spaced apart from each other, a gate electrode extending in a second direction to intersect the active region and partially surrounding the plurality of channel layers, and a source/drain region on the active region on at least one side of the gate electrode and in contact with the plurality of channel layers, and extending from the sidewalls of the active region having a major width in the second direction in a first region adjacent to a lowermost channel layer adjacent to the active region among the plurality of channel layer.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims benefit of priority to Korean Patent ApplicationNo. 10-2019-0061678 filed on May 27, 2019 in the Korean IntellectualProperty Office, the disclosure of which is incorporated herein byreference in its entirety.

BACKGROUND

The present disclosure relates to a semiconductor device.

As demand for high-performance, high-speed, and/or multifunctionalsemiconductor devices increases, the degree of integration ofsemiconductor devices has also increased. In the manufacturing ofsemiconductor devices having micropatterns in line with a trend for highdegrees of integration in semiconductor devices, it may be advantageousto implement patterns having relatively fine widths and/or spacings.Various efforts to develop semiconductor devices, includingthree-dimensional channels, have been made to overcome limitations inoperating characteristics resulting from miniaturization and/orreduction of planar metal oxide semiconductor FETs (MOSFETs).

SUMMARY

Example embodiments provide a semiconductor device having improvedelectrical characteristics.

According to an example embodiment, a semiconductor device includes anactive region on a substrate extending in a first direction, the activesurface having an upper surface and sidewalls, a plurality of channellayers disposed on the active region to be vertically spaced apart fromeach other, a gate electrode extending in a second direction tointersect the active region and partially surrounding the plurality ofchannel layers, and a source/drain region on the active region on atleast one side of the gate electrode and in contact with the pluralityof channel layers. The source/drain region extends from the sidewalls ofthe active region and has a widest local width at the major width in thesecond direction in a first region adjacent to a lowermost channel layeradjacent to the active region among the plurality of channel layer.

According to an example embodiment, a semiconductor device includes anactive region extending on a substrate in a first direction, first andsecond channel layers sequentially vertically spaced apart from eachother above the active region, a gate electrode extending in a seconddirection to intersect the active region on the substrate andsurrounding the first and second channel layers, and a source/drainregion on the active region on at least one side of the gate electrodeand disposed to be in contact with the first and second channel layers.The source/drain region has a first major width in the second directionin a region adjacent to the first channel layer and has a second majorwidth, less than the first major width, in the second direction in aregion adjacent to the second channel layer.

According to an example embodiment, a semiconductor device includes anactive region extending on a substrate in a first direction, the activeregion having an upper surface and sidewalls, a gate electrode extendingin a second direction to intersect the active region on the substrate, aplurality of channel layers on the active region to be vertically spacedapart from each other in a region in which the active region and thegate electrode intersect each other, spacer layers on the sidewalls ofthe active region in the second direction and exposing the upper surfaceand portions of the sidewalls of the active region, and a source/drainregion on the active region on at least one side of the gate electrodeand in contact with the plurality of channel layers. The source/drainregion extends from the sidewalls of the active region, exposed by thespacer layers, to be inclined with respect to an upper surface of thesubstrate to have a width extending from both sides of the activeregion.

BRIEF DESCRIPTION OF DRAWINGS

The above and other aspects, features, and advantages of the presentdisclosure will be more clearly understood from the following detaileddescription, taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 is a top view of a semiconductor device according to exampleembodiments;

FIG. 2 is a cross-sectional view of a semiconductor device according toexample embodiments;

FIGS. 3A and 3B are a top view and a cross-sectional view of asemiconductor device according to example embodiments, respectively;

FIG. 4 is a cross-sectional view of a semiconductor device according toexample embodiments;

FIGS. 5A to 5C are cross-sectional views of a semiconductor deviceaccording to example embodiments;

FIG. 6 is a cross-sectional view of a semiconductor device according toexample embodiments; and

FIGS. 7A to 7J are cross-sectional views illustrating a method ofmanufacturing a semiconductor device according to example embodiments.

DETAILED DESCRIPTION

Hereinafter, example embodiments will be described with reference to theaccompanying drawings.

FIG. 1 is a top view of a semiconductor device according to exampleembodiments.

FIG. 2 is a cross-sectional view of a semiconductor device according toexample embodiments. FIG. 2 illustrates cross sections taken along linesI-I′, II-IT, and III-III′ of the semiconductor device of FIG. 1. Forbrevity of description, only main components of the semiconductor deviceare illustrated in FIGS. 1 and 2.

Referring to FIGS. 1 and 2, a semiconductor device 100 may include asubstrate 101, active regions 105 on the substrate 101, channelstructures 140, each including a plurality of channel layers 141, 142,and 143 disposed on the active regions 105 to be vertically spaced apartfrom each other, source/drain regions 150 in contact with the pluralityof channel layers 141, 142, and 143, gate structures 160 extended tointersect the active region 105, and/or contact plugs 180 connected tothe source/drain regions 150. The semiconductor device 100 may furtherinclude isolation layers 110, internal spacer layers 130, and/or aninterlayer insulation layer 190. The gate structure 160 may include agate dielectric layer 162, a gate electrode 165, spacer layers 164,and/or a gate capping layer 166.

In the semiconductor device 100, the active regions 105 may have a finstructure, and the gate electrode 165 may be disposed between the activeregion 105 and the channel structure 140 and between the plurality ofchannel layers 141, 142, and 143 of the channel structures 140.Accordingly, the semiconductor device 100 may include a MBCFET™ (MultiBridge Channel FET) formed by the channel structures 140, thesource/drain regions 150, and the gate structures 160.

The substrate 101 may have an upper surface extending in an x directionand a y direction. The substrate 101 may include a semiconductormaterial such as a group IV semiconductor, a group III-V compoundsemiconductor, or a group II-VI compound semiconductor. For example, thegroup IV semiconductor may include silicon, germanium or silicongermanium. The substrate 101 may be provided as a bulk wafer, anepitaxial layer, a silicon on insulator (SOI) layer, a semiconductor oninsulator (SeOI) layer, or the like.

The active region 105 may be defined in the substrate 101 by theisolation layers 110 and may be disposed to extend in a first direction,for example, the x direction. The active region 105 may have an activefin structure protruding from the substrate 101. The active region 105may be disposed such that an upper end thereof protrudes from topsurfaces of the isolation layers 110 by a predetermined height. Theactive region 105 may include a portion of the substrate 101, or mayinclude an epitaxial layer grown from the substrate 101. A portion ofthe active region 105 on the substrate 101 may be recessed on oppositesides adjacent to the gate structure 160, and the source/drain region150 may be disposed on the recessed portion of the active region 105.Accordingly, the active region 105 may have a relatively greater heightbelow the channel structure 140 and the gate structure 160, asillustrated in FIG. 2. In some embodiments, the active region 105 mayinclude impurities, and at least portions of the active regions 105 mayinclude impurities having conductivity types opposite to each other, butan example embodiment of the active regions 105 is not limited thereto.

The isolation layer 110 may define the active region 105 on thesubstrate 101. The isolation layer 110 may be formed by, for example, ashallow trench isolation (STI) process. The isolation layer 110 may beformed to expose upper sidewalls of the active regions 105. In someembodiments, the isolation layer 110 may include a region extendingdeeper to a lower portion of the substrate 101 between the activeregions 105. The isolation layer 110 may have a curved top surfacehaving a level becoming higher in a direction to the active region 105,but a shape of the top surface of the isolation layer 110 is not limitedthereto. The isolation layer 110 may be formed of an insulatingmaterial. The isolation layer 110 may be, for example, an oxide, anitride, or a combination thereof. As illustrated in FIG. 2, theisolation layer 110 may have different heights of the top surface belowand outside of the gate structure 160. Such variation in shape is formeddepending on the manufacturing process, and the height difference of thetop surface may be changed according to example embodiments.

The channel structure 140 includes first to third channel layers 141,142, and 143, a plurality of channel layers, disposed on the activeregion 105 to be spaced apart from each other in a directionperpendicular to the top surface of the active region 105, for example,a z direction. The first to third channel layers 141, 142, and 143 maybe spaced apart from the top surface of the active region 105 whilebeing connected to the source/drain regions 150. Each of the first tothird channel layers 141, 142, and 143 may have a width equal or similarto a width of the active region 105 in a y direction, and may have awidth equal or similar to a width of the gate structure 160 in the xdirection. However, in some embodiments, the first to third channellayers 141, 142, and 143 may have decreased widths such that sidesurfaces thereof are disposed below the gate structure 160 in the xdirection. Each of the first to third channel layers 141, 142, and 143may be formed of a semiconductor material and may include at least oneof silicon (Si), silicon germanium (SiGe), and germanium (Ge). The firstto third channel layers 141, 142, and 143 may be formed of, for example,the same material as that of the substrate 101. The number and shape ofthe channel layers 141, 142, and 143, constituting a single channelstructure 140, may be variously changed according to exampleembodiments.

The source/drain regions 150 may be disposed on active regions 105 atopposite sides adjacent to the gate structure 160. The source/drainregions 150 may be provided as a source region or a drain region of atransistor. Each of the source/drain regions 150 may be disposed suchthat an upper surface thereof is higher than an uppermost surface of thechannel structure 140, and may be an elevated source/drain disposed tobe higher than a bottom surface of the gate electrode 165 on the channelstructure 140.

The source/drain regions 150 may be disposed on a region in which aportion of the active region 105 is recessed between the channelstructures 140 and the gate structures 160 adjacent to each other in thex direction. The source/drain regions 150 may extend from a sidewall ofthe active region 105 to be inclined with respect to an upper surface ofthe substrate 101 at opposite sides adjacent to the gate structure 160,as illustrated in a cross-section view taken in the y direction. Thesource/drain regions 150 may have a major width in the y direction in aregion disposed adjacent to the first channel layer 141, a lowermostlayer adjacent to the active region 105 among the plurality of channellayers 141, 142, and 143, for example, a region, disposed adjacent tothe first channel layer 141 in the direction, having a heightcorresponding to a height of the first channel layer 141. Thesource/drain regions 150 may have relatively decreased widths in regionsdisposed adjacent to the overlying first and second channel layers 142and 143, for example, regions, disposed adjacent to the second and thirdchannel layers 142 and 143, each having a height corresponding to aheight at which the second and third channel layers 142 and 143 aredisposed. In the source/drain regions 150, an inclined surface,extending from the sidewall of the active region 105, may be a facetprovided along a crystal plane, for example, a <111> facet. Shapes ofthe source/drain regions 150 will be described in further detail laterwith reference to FIGS. 3A to 5.

The source/drain regions 150 may be formed of a semiconductor material.For example, the source/drain regions 150 may include at least one ofsilicon germanium (SiGe), silicon (Si), silicon arsenic (SiAs), siliconphosphide (SiP), and silicon carbide (SiC). Specifically, thesource/drain regions 150 may be formed of an epitaxial layer. Forexample, the source/drain regions 150 may include n-type doped silicon(Si) and/or p-type doped silicon germanium (SiGe). In exampleembodiments, the source/drain regions 150 may include a plurality ofregions including elements having different concentrations, and/ordoping elements. In addition, in example embodiments, the source/drainregions 150 are connected to each other on two or more active regions105 disposed adjacent to each other, or may be merged to form a singlesource/drain region 150.

The gate structure 160 may be disposed to intersect the active regions105 and the channel structures 140 above the active regions 105 and thechannel structures 140 to extend in one direction, for example, the ydirection. Channel region of transistors may be formed in the activeregions 105 and the channel structures 140 intersecting the gatestructure 160. The gate structure 160 includes a gate electrode 165, agate dielectric layer 162 between the gate electrode 165 and theplurality of channel layers 141, 142, and 143, spacer layers 164 on sidesurfaces of the gate electrode 165, and a gate capping layer 166 on atop surface of the gate electrode 165.

The gate dielectric layer 162 may be disposed between the active region105 and the gate electrode 165 and between the channel structure 140 andthe gate electrode 165, and may be disposed to cover at least a portionof a surface of the gate electrode 165. For example, the gate dielectriclayer 162 may be disposed to surround all surfaces except for anuppermost surface of the gate electrode 165. The gate dielectric layer162 may extend between the gate electrode 165 and the spacer layers 164,but extension of the gate dielectric layer 162 is not limited thereto.The gate dielectric layer 162 may include an oxide, a nitride, or ahigh-k material. The high-k material may refer to a dielectric materialhaving a dielectric constant higher than a dielectric constant ofsilicon oxide (SiO₂). The high-k material may include one of, forexample, aluminum oxide (Al₂O₃), tantalum oxide (Ta₂O₃), titanium oxide(TiO₂), yttrium oxide (Y₂O₃), zirconium oxide (ZrO₂), zirconium siliconoxide (ZrSi_(x)O_(y)), hafnium oxide (HfO₂), hafnium silicon oxide(HfSi_(x)O_(y)), lanthanum oxide (La₂O₃), lanthanum aluminum oxide(LaAl_(x)O_(y)), lanthanum hafnium oxide (LaHf_(x)O_(y)), hafniumaluminum oxide (HfAl_(x)O_(y)), and praseodymium oxide (Pr₂O₃).

The gate electrode 165 may be disposed over the active region 105 toextend to an upper portion of the channel structure 140 while fillingspaces between the plurality of channel layers 141, 142, and 143. Thegate electrode 165 may be spaced apart from the plurality of channellayers 141, 142, and 143 by the gate dielectric layer 162. The gateelectrode 165 may include a conductive material, and may include a metalnitride such as titanium nitride (TiN), tantalum nitride (TaN), or atungsten nitride (WN), and/or a metal material such as aluminum (Al),tungsten (W), or molybdenum (Mo), or a semiconductor material such asdoped polysilicon. The gate electrode 165 may have a multilayerstructure including two or more layers. The gate electrode 165 may bedivided between at least some of adjacent transistors by an additionaldivision portion, depending on the configuration of the semiconductordevice 100.

The spacer layers 164 may be disposed on both side surfaces of the gateelectrode 165 on the channel structure 140. The spacer layers 164 mayinsulate the source/drain regions 150 and the gate electrodes 165 fromeach other, together with internal spacer layers 130. In someembodiments, the spacer layers 164 may have a multilayer structure. Thespacer layers 164 may include an oxide, a nitride, and oxynitrides.Specifically, the spacer layers 164 may include a low-k dielectriclayer. Active spacer layers 164F may be formed simultaneously in thesame process as the spacer layers 164, and thus, may include the samematerial as the spacer layers 164. The active spacer layers 164F may bedisposed on the upper sidewalls of the active regions 105 exposed by theisolation layers 110 at opposite sides adjacent to the gate structure160.

The gate capping layer 166 may be disposed on an uppermost surface ofthe gate electrode 165, and a lower surface and side surfaces thereofmay be surrounded by the gate electrode 165 and the spacer layers 164,respectively. The gate capping layer 166 may include an oxides, anitrides, and an oxynitride.

The internal spacer layers 130 may be disposed parallel to the gateelectrode 165 between spaces of the channel structure 140. Below thethird channel layer 143, the gate electrode 165 may be spaced apart fromthe source/drain regions 150 by the internal spacer layers 130 to beelectrically insulated from the source/drain regions 150. The internalspacer layers 130 may have a shape in which a side surface, facing thegate electrode 165, is convexly rounded inwardly toward the gateelectrode 165, but a shape of the internal spacer layers is not limitedthereto. The internal spacer layers 130 may include an oxide, a nitride,and an oxynitride. Specifically, the internal spacer layers 130 mayinclude a low-k dielectric layer. In some embodiments, the internalspacer layers 130 may be omitted. In this case, the gate electrode 165may be disposed to extend between the spaces of the channel structure140, and a side surface of the gate electrode 165 along the x directionmay be disposed to be vertically parallel to a side surface of thechannel structure 140.

The interlayer insulation layer 190 may be disposed to cover topsurfaces of the source/drain regions 150, the gate structures 160, andthe isolation layers 110. The interlayer insulation layer 190 mayinclude at least one of, for example, an oxide, a nitride, and anoxynitride, and may include a low-k dielectric material.

The contact plug 180 may be connected to the source/drain region 150 toapply an electrical signal to the source/drain region 150. The contactplug 180 may penetrate through the interlayer insulation layer 190 tovertically extend. The contact plug 180 may be disposed on thesource/drain region 150, as illustrated in FIG. 1. In some embodiments,the contact plug 180 may be disposed to have a length greater than alength of the source/drain region 150 in the y direction. The contactplug 180 may have an inclined side surface, having a lower portionnarrower than an upper portion, depending on an aspect ratio, but ashape of the contact plug 180 is not limited thereto.

The contact plug 180 may be disposed to recess the source/drain region150 to a predetermined depth. The contact plug 180 may extend to, forexample, a portion lower than the third channel layer 143. The contactplug 180 may be recessed to, for example, an upper surface of the secondchannel layer 142, but recessing of the contact plug 180 is not limitedthereto. In example embodiments, the contact plug 180 may be disposed tobe in contact with the source/drain region 150 along the top surface ofthe source/drain region 150 without recessing the source/drain region150.

FIGS. 3A and 3B are a top view and a cross-sectional views of asemiconductor device according to example embodiments, respectively.FIGS. 3A and 3B illustrate an enlarged version of region ‘A’ of FIG. 1and an enlarged version of region ‘B’ of FIG. 2, respectively.

Referring to FIGS. 3A and 3B, the source/drain region 150 may extendfurther than the active region 105, to opposite sides adjacent to thegate structure 160 in the y direction and may include a plurality ofregions, each having a width greater than a width of the active region105. The source/drain region 150 has a first region including a firstpoint P1 having a first major width W1 from a lower portion thereof, asecond region including a second point P2 having a second major width W2less than the first major width W1, and a third region P3 having a thirdmajor width W3 less than the first major width W1. The first major widthW1 of the first point P1 may be a major width of the first region in they direction and may be a major width of the entire source/drain region150 in the y direction. The source/drain region 150 may have a widthgreater than the active region 105 at least in the first to third pointsP1, P2, and P3, and thus, may have a curvature. The shape of thesource/drain region 150 may result from the fact that a lower portion ofthe source/drain region 150 is grown from the sidewall of the activeregion 105 and an upper portion of the source/drain region 150 hasregions in which growth of the source/drain region 150 is limited due tothe internal spacer layers 130 described with reference to FIGS. 1 and2.

The first point P1 may be a point in which the source/drain region 150is grown from the top surface and the sidewalls of the active region 105and grown from the side surface of the first channel layer 141 in the xdirection to have a major width. Specifically, the source/drain region150 may be grown from the sidewall of the active region 105 to the firstpoint P1 while forming a facet provided along a crystal plane.Accordingly, in the source/drain region 150, a side surface extending tothe first point P1 may form a specific angle θ depending on a crystalplane. For example, when forming a [111] facet, the angle θ may be about54.7 degrees. A side surface of an upper portion of the first point P1may also be a facet depending on a crystal plane. Accordingly, sidesurfaces of upper and lower portions on the basis of the first point P1may be facets, and the source/drain region 150 may have the major widthon a boundary between the facets. The first point P1 may be disposed ata height between the first channel layer 141 and the active region 105,but a detailed height may be variously changed in example embodiments.For example, the first point P1 may be disposed at a height between anupper surface of the first channel layer 141 and an upper surface of theactive region 105. For example, the first point P1 may be disposed at aheight between a lower surface of the first channel layer 141 and anupper surface of the active region 105. The location of the first pointP1 may be controlled by a first length L1, at which the sidewall of theactive region 105 is exposed by active spacer layers 164F, and a secondlength L2, a length between the top surface of the active region 105 anda lower surface of the first channel layer 141. The second length L2 maybe controlled by a depth at which the active region 105 is recessed inthe source/drain region 150 during a manufacturing process.

When a length from a point, in which the active region 105 is exposed,to a height of a middle of the first and second channel layers 141 and142 is defined as a third length L3, a fourth length L4, at which thefirst point P1 protrudes from an extension line of a side surface of thefirst channel layer 141 or the active region 105 in the y direction, maybe approximately calculated by (L3/2)/tan θ. Accordingly, the fourthlength L4 may be increased as a first length L1, at which the sidewallof the active region 105 is exposed by the active spacer layers 164F,and a second length L2 between the top surface of the active region 105and the lower surface of the first channel layer 141 are increased. Inexample embodiments, the fourth length L4 may range from about 7 nm to20 nm. When a length, at which the second point P2 protrudes from anextension line of a side surface of the second channel layer 142 or theactive region 105 in the y direction, is defined as a fifth length L5,the length L5 may also be calculated in a manner similar to thecalculation manner of the fourth length L4. In example embodiments, aratio of the fifth length L5 to the fourth length L4 (L5/L4) may rangefrom about 0.4 to about 0.7. The range may be controlled by changingthicknesses and a spacing distance of the first and second channellayers 141 and 142 and the first and second lengths L1 and L2.

The second point P2 and the third point P3 may be disposed at heightscorresponding to the second channel layer 142 and the third channellayer 143, respectively. As illustrated in FIG. 3A, the second point P2and the third point P3 may be disposed in substantially the sameposition on a plane. For example, the second major width W2 and thethird major width W3 may be substantially the same, but are not limitedthereto. According to embodiments, the third major width W3 may be lessthan the second major width W2. In this case, the first point P1, thesecond point P2, and the third point P3 may be sequentially disposedfrom outside of the source/drain region 150 in the y direction on aplane.

The source/drain region 150 may include regions, each having a decreasedwidth, between the first to third points P1, P2, and P3. For example,the source/drain region 150 may include regions, each having a decreasedwidth between the first point P1 and the second point P2 and between thesecond point P2 and the third point P3 and regions, each having a localminimum width. The minimum width may be proximate to, for example, thewidth of the active region 105, but is not limited thereto. The regions,each locally having a minimum width, may be disposed at a heightcorresponding to, for example, a height at which the internal spacerlayers 130 are disposed. Accordingly, the source/drain region 150 mayhave a curvature corresponding to dispositions of the plurality ofchannel layers 141, 142, and 143 and internal spacer layers 130, and mayhave a gently curved top surface above the third point P3. Asillustrated in FIG. 3B, the source/drain region 150 may have an externalside surface having facets in at least one region between the first tothird points P1, P2, and P3.

FIG. 4 is a cross-sectional view of a semiconductor device according toexample embodiments. FIG. 4 illustrates an enlarged version of a regioncorresponding to the region ‘B’ of FIG. 2.

Referring to FIG. 4, various types of contact plugs 180, 180 a, and 180b according to example embodiments are illustrated together with asource/drain region 150 and a contact plug 180 to describe a disposingrelationship between the source/drain region 150 and the contact plug180.

The contact plugs 180, 180 a, and 180 b may be disposed to recess anupper portion of the source/drain region 150 to a predetermined depth RDfrom an upper surface thereof. The recessed depth RD may be a heightsubstantially corresponding to an upper surface of a second channellayer 142. However, the recessed depth RD is not limited thereto and maybe variously changed in example embodiments. A person having ordinaryskill the art would know when the recessed depth RD is relatively large,the source/drain region 150 may be decreased in volume to insufficientlyperform electrical functions. When the recessed depth RD is relativelysmall, the source/drain region 150 and the contact plugs 180, 180 a, and180 b may not be electrically connected to each other due to a processvariation.

The contact plugs 180, 180 a, and 180 b according to example embodimentsmay have different widths, which are sequentially increased in the ydirection. Similarly to the contact plug 180 b, when the contact plug180 b has a width greater than a width of the source/drain region 150 incontact with the contact plug 180 b, an upper portion of thesource/drain region 150 is removed at opposite sides adjacent to a gatestructure 160 by the recessed depth RD. Accordingly, in an ultimatestructure of a semiconductor device, a shape of the source/drain region150 may also be different depending on widths of the contact plugs 180,180 a, and 180 b.

FIGS. 5A to 5C are cross-sectional views of a semiconductor deviceaccording to example embodiments. FIGS. 5A to 5C illustrate enlargedversions of a region corresponding to the region ‘B’ of FIG. 2,respectively.

Referring to FIG. 5A, a source/drain region 150 a may have a shape inwhich facets are generally alleviated while including first to thirdpoints P1, P2, and P3, each having a locally large width, and includingthe first point P1 having a major width, as illustrated in FIG. 3A. Forexample, the source/drain region 150 a may have a curvaturecorresponding to a plurality of channel layers 141, 142, and 143. Such ashape may be controlled depending on a material of the source/drainregion 150 a. For example, when the source/drain region 150 a includesimpurities occupying an interstitial site, the source/drain region 150 amay be grown to have such a curved external surface. In this case, thesource/drain region 150 a may be formed of, for example, siliconphosphide (SiP).

Referring to FIG. 5B, a source/drain region 150 b may have a box-shapedupper portion which does not include a third point P3 while includingfirst and points P1 and P2, each having a locally large width, andincluding the first point P1 having a major width, as illustrated inFIG. 3A. The source/drain region 150 b may have a fourth width W4,smaller than a first width W1 of the first point P1, at a heightcorresponding to a third channel layer 143. The fourth width W4 may besmaller than a second width W2 a of the second point P2, or may besimilar to the second width W2 a. Even in this case, the source/drainregion 150 b may have an inclined surface up to the first point P1having a major width.

Referring to FIG. 5C, a source/drain region 150 c may be disposed suchthat a portion of the source/drain region 150 c is grown onto activespacer layers 164F from a lower end thereof to contact the active spacerlayers 164F. Accordingly, the source/drain region 150 c may have ashape, in which a surface extending from a sidewall of an active region105 to a first point P1 includes a plurality of surfaces or curvedsurfaces rather than a single facet, while including the first point P1having a major width. Such a shape of the source/drain region 150 c mayappear when a lower end portion thereof is not grown along a crystalplane under growth conditions of the source/drain region 150 c. An upperportion of the source/drain region 150 c is provided with second andthird points P2 and P3, each having a locally large width, but thesource/drain region 150 c may have a box shape, as illustrated in FIG.5B, in some embodiments.

FIG. 6 is a cross-sectional view of a semiconductor device according toexample embodiments. FIG. 6 illustrates a region corresponding to across section taken along line II-IT of FIG. 1.

Referring to FIG. 6, a semiconductor device 100 a may include an activeregion 105 a and a channel structure 140 a having widths different fromthose in the example embodiment of FIG. 2. The active region 105 a andthe channel structure 140 a may have relatively smaller widths, suchthat a plurality of channel layers 141 a, 142 a, and 143 a of thechannel structure 140 a may each have a circular shape or an ellipticalshape, in which a difference between lengths of a major axis and a minoraxis is relatively small, on a cross section in a y direction. Forexample, in the example embodiment of FIG. 2, each of the plurality ofchannel layers 141, 142, and 143 may have a width of about 20 nm to 50nm in the y direction and, in this embodiment, each of the plurality ofchannel layers 141 a, 142 a, and 143 a may have a width of about 3 nm to12 nm in the y direction. As described above, in example embodiments,widths and shapes of the active region 105 a and the channel structure140 a may be variously changed.

FIGS. 7A to 7J are cross-sectional views illustrating a method ofmanufacturing a semiconductor device according to example embodiments.In FIGS. 7A to 7J, an example embodiment of a method of manufacturingthe semiconductor device of FIGS. 1 and 2 will be described and crosssections corresponding to FIG. 2 are illustrated.

Referring to FIG. 7A, sacrificial layers 120 and channel layers 141,142, and 143 may be alternately stacked on a substrate 101.

The sacrificial layers 120 may be layers replaced with a gate dielectriclayer 162 and a gate electrode 165 in a subsequent process, asillustrated in FIG. 2. The sacrificial layers 120 may be formed of amaterial having an etching selectivity with respect to the channellayers 141, 142, and 143. The channel layers 141, 142, and 143 mayinclude a material different from a material of the sacrificial layers120. The sacrificial layers 120 and channel layers 141,142 and 143include a semiconductor material including at least one of silicon (Si),silicon germanium (SiGe), and germanium (Ge) and may include differentmaterials. The sacrificial layers 120 and channel layers 141,142 and 143may or may not include impurities. For example, the sacrificial layers120 may include silicon germanium (SiGe), and the channel layers 141,142 and 143 may include silicon (Si).

The sacrificial layers 120 and the channel layers 141, 142, and 143 maybe formed by performing an epitaxial growth process using the substrate101 as a seed. Each of the sacrificial layers 120 and channel layers141, 142, and 143 may have a thickness ranging from about 1 {acute over(Å)} to 100 nm. The number of the channel layers 141, 142, and 143,stacked alternately with the sacrificial layer 120, may be variouslychanged in example embodiments.

Referring to FIG. 7B, a stacked structure of the sacrificial layers 120and the channel layers 141, 142, and 143 and a portion of the substrate101 may be removed to form active structures.

The active structure may include sacrificial layers 120 and channellayers 141, 142, and 143 alternately stacked with each other. The activestructure may further include active regions 105 formed by removing aportion of the substrate 101 to protrude to an upper surfaced of thesubstrate 101. The active structures may be formed in a linear shapeextending in one direction, for example, the x direction in FIG. 1, andmay be spaced apart from each other in the y direction.

In a region in which a portion of the substrate 101 is removed,isolation layers 110 may be formed by filling the region with aninsulating material and recessing the insulating material such that theactive regions 105 protrude. Top surfaces of the isolation layers 110may be formed to be lower than top surface of the active regions 105.

Referring to FIG. 7C, sacrificial gate structures 170 and spacer layers164 may be formed on the active structures.

Each of the sacrificial gate structures 170 may be a sacrificialstructure formed in a region, in which a gate dielectric layer 162 and agate electrode 165 are disposed above the channel structures 140, in asubstrate process, as illustrated in FIG. 2. The sacrificial gatestructure 170 may include first and second sacrificial gate layers 172and 175, and a mask pattern layer 176, which are sequentially stacked.The first and second sacrificial gate layers 172 and 175 may bepatterned using a mask pattern layer 176. The first and secondsacrificial gate layers 172 and 175 may be respectively an insulatinglayer and a conductive layer, but are not limited thereto. The first andsecond sacrificial gate layers 172 and 175 may be provided as a singlelayer. For example, the first sacrificial gate layer 172 may include asilicon oxide and the second sacrificial gate layer 175 may includepolysilicon. The mask pattern layer 176 may include a silicon oxideand/or a silicon nitride. The sacrificial gate structures 170 may have alinear shape extending in one direction while intersecting the activestructures. The sacrificial gate structures 170 may extend, for example,in the y direction of FIG. 1 and be spaced apart from each other in thex direction.

The spacer layers 164 may be formed on both sidewalls of the sacrificialgate structures 170. With the spacer layers 164, active spacer layers164F may also be formed on both sidewalls of the active structuresexposed from the sacrificial gate structures 170. The spacer layers 164and the active spacer layers 164F may be formed by forming a layerhaving a uniform thickness along top and side surfaces of thesacrificial gate structures 170 and the active structures andanisotropically etching the layer having a uniform thickness. The spacerlayers 164 and the active spacer layers 164F may be formed of the samematerial. The spacer layers 164 and the active spacer layers 164F may beformed of a low-k dielectric material and may include at least one of,for example, SiO, SiN, SiCN, SiOC, SiON, and SiOCN.

Referring to FIG. 7D, the sacrificial layers 120 and channel layers 141,142, and 143 exposed between sacrificial gate structures 170 may beremoved to form channel structures 140.

The exposed sacrificial layers 120 and the exposed channel layers 141,142, and 143 may be removed using the sacrificial gate structures 170and spacer layers 164 as masks. Accordingly, the channel layers 141,142, and 143 each may have a limited length in the x direction andconstitute the channel structure 140. In example embodiments, portionsof the sacrificial layers 120 and a portion of the channel structure 140may be removed from side surfaces thereof below the sacrificial gatestructures 170, such that both sides thereof may be disposed below thesacrificial gate structures 170 and the spacer layers 164.

In this process, portions of the active regions 105 may also be recessedand removed from top surfaces thereof. In addition, portions of theactive spacer layers 164F, disposed on both sidewalls of the activestructures, are removed while the sacrificial layers 120 and channellayers 141, 142, and 143 are removed, and portions thereof may befurther removed during a process of recessing the active regions 105.

The active spacer layers 164F are controlled to remain by changingconditions of the processes such that upper sidewalls of the activeregions 105 are exposed by a predetermined length L1, as illustrated inthe drawing. According to embodiments, the length L1 may be variedwithin a range of exposing the upper sidewalls of the active regions105. According to embodiments, in this process, portions of the spacerlayers 164 on both sidewalls of the sacrificial gate structures 170 mayalso be removed from upper portions thereof to a predetermined depth. Inexample embodiments, the active spacer layers 164F may be removedthrough an additional process to be formed in such a manner.

Referring to FIG. 7E, portions of the exposed sacrificial layers 120 maybe removed from side surfaces thereof.

The sacrificial layers 120 may be etched selectively with respect to thechannel structures 140 by, for example, a wet etching process, to beremoved from the side surfaces thereof to a predetermined depth in thex-direction. The sacrificial layers 120 may have inwardly recessed sidesurfaces due to such side etching. However, shapes of the side surfacesof the sacrificial layers 120 are not limited to those illustrated inthe drawing.

Referring to FIG. 7F, internal spacer layers 130 may be formed inregions in which the sacrificial layers 120 are removed.

The internal spacer layers 130 may be formed by filling the regions, inwhich the sacrificial layers 120 are removed, with an insulatingmaterial and removing the insulating material deposited on outside ofthe channel structures 140. The internal spacer layers 130 may be formedof the same material as the spacer layers 164, but a material of theinternal spacer layers 130 is not limited thereto. For example, theinternal spacer layers 130 may include at least one of SiN, SiCN, SiOCN,SiBCN, and SiBN.

When the active spacer layers 164F are formed to be higher than theupper sidewalls of the active regions 105, rather than being formed toexpose the upper sidewall of the active regions 105 in the above processreferring to FIG. 7D, a material of the internal spacer layers 130 mayremain between the active spacer layers 164F and the active region 105in this process. In this case, growth of the source/drain regions 150may be hampered and the volume of the source/drain regions 150 may bedecreased in a subsequent process to degrade electrical characteristicsof the semiconductor device. However, according to example embodiments,since the active spacer layers 164F are formed to expose the uppersidewalls of the active regions 105, the material of the internal spacerlayers 130 does not remain in regions, in which the source/drain regions150 are to be formed, in this process. Therefore, the growth of thesource/drain regions 150 may not be hampered.

Referring to FIG. 7G, source/drain regions 150 may be formed on activeregions 105 at opposite sides adjacent to the sacrificial gatestructures 170.

The source/drain regions 150 may be formed by performing a selectiveepitaxial growth process using the active regions 105 and the channelstructures 140 as seeds. The source/drain regions 150 may be connectedto the channel layers 141, 142, and 143 of the channel structures 140through side surfaces thereof and may be in contact with the internalspacer layers 130 between the channel layers 141, 142, and 143.

Since the source/drain regions 150 are grown from the sidewalls of theactive regions 105 on a cross section in a y direction, each of thesource/drain regions 150 may be grown with a facet provided along acrystal plane in an epitaxial growth process. For example, thesource/drain regions 150 may be grown to form a side surface inclinedwith respect to an upper surface of the active regions 105 while beinggrown on a (100) plane, the top surface of the active regions 105, at arelatively high speed in a direction perpendicular to the top surface.Thus, the source/drain regions 150 may include a region having a majorwidth, disposed between the source/drain regions 150 and the firstchannel layer 141. The source/drain regions 150 may include impuritiesdoped during the growth process or after the growth process.

Referring to FIG. 7H, an interlayer insulation layer 190 may be formed,and the sacrificial layers 120 and the sacrificial gate structures 170may be removed.

The interlayer insulation layer 190 may be formed by forming aninsulating layer to cover the sacrificial gate structures 170 and thesource/drain regions 150 and performing a planarization process.

The sacrificial layers 120 and the sacrificial gate structures 170 maybe selectively removed with respect to the spacer layers 164, theinterlayer insulation layer 190, and the channel structures 140. Afterthe sacrificial gate structures 170 are removed to form upper gapregions UR, the sacrificial layers 120, exposed through the upper gapregions UR, may be removed to form lower gap regions LR. For example,when the sacrificial layers 120 includes silicon germanium (SiGe) andthe channel structures 140 includes silicon (Si), the sacrificial layers120 may be selectively removed by performing a wet etching process usinga peracetic acid as an etchant. During the removal process, thesource/drain regions 150 may be protected by an interlayer insulationlayer 190 and the internal spacer layers 130.

Referring to FIG. 7I, gate dielectric layers 162 may be formed in theupper gap regions UR and the lower gap regions LR.

The gate dielectric layers 162 may be formed to conformally coverinternal surfaces of the upper gap regions UR and the lower gap regionsLR.

Referring to FIG. 7J, gate electrodes 165 may be formed to fill theupper and lower gap regions UR and LR, and a gate capping layer 166 maybe formed on the gate electrodes 165.

After the gate electrodes 165 are formed to completely fill the uppergap regions UR and the lower gap regions LR, they may be removed fromupper portion thereof in the upper gap regions UR to a predetermineddepth. The gate capping layer 166 may be formed in the region in whichthe gate electrodes 165 are removed in the upper gap regions UR. Thus,gate structures 160, including the gate dielectric layer 162, the gateelectrode 165, the spacer layers 164, and the gate capping layer 166,may be formed.

Next, referring to FIG. 2, contact plugs 180 may be formed.

First, the interlayer insulation layer 190 may be patterned to formcontact holes, and a conductive material may fill the contact holes toform the contact plugs 180. The contact holes may be formed by removingthe interlayer insulation layer 190 at opposite sides adjacent to thegate structure 160 using an additional mask layer such as a photoresistpattern. Bottom surfaces of the contact holes may be recessed into thesource/drain regions 150 or may have a curvature along the top surfaceof the source/drain regions 150. In example embodiments, shapes anddispositions of the contact plugs 180 may be variously changed.

As described above, a structure and a shape of a source/drain region maybe controlled to provide a semiconductor device having improvedelectrical characteristics.

While example embodiments have been shown and described above, it willbe apparent to those skilled in the art that modifications andvariations could be made without departing from the scope of the presentinventive concept as defined by the appended claims.

What is claimed is:
 1. A semiconductor device comprising: an activeregion on a substrate extending in a first direction, the active regionhaving an upper surface and sidewalls; a plurality of channel layers onthe active region to be vertically spaced apart from each other; a gateelectrode extending in a second direction to intersect the active regionand surrounding the plurality of channel layers; and a source/drainregion on the active region on at least one side of the gate electrode,capping the plurality of channel layers along the at least one side ofthe gate electrode, and extending from the sidewalls of the activeregion having a major width in the second direction between firstprotruding points in a first region adjacent to a lowermost channellayer adjacent to the active region among the plurality of channellayers, wherein the source/drain region has a width smaller than themajor width in a region above the first region, and the first protrudingpoints protrude, in the second direction, further than second protrudingpoints in the region above the first region.
 2. The semiconductor deviceof claim 1, wherein the plurality of channel layers include first tothird channel layers stacked sequentially from the active region, andthe first region is higher than the upper surface of the active regionand lower than an upper surface of the first channel layer.
 3. Thesemiconductor device of claim 2, wherein the source/drain region has afirst major width that is the major width, in the first region, and hasa second major width, less than the first major width, in a secondregion having a height corresponding to a height at which the thirdchannel layer is disposed.
 4. The semiconductor device of claim 3,wherein the source/drain region includes a region having a third width,less than the first major width and the second major width, between thefirst region and the second region.
 5. The semiconductor device of claim3, wherein the source/drain region has a fourth major width, less thanthe first major width, in a third region having a height correspondingto a height at which the second channel layer is disposed.
 6. Thesemiconductor device of claim 1, wherein the source/drain region has afirst surface extending from the sidewall of the active region inclinedwith respect to the upper surface of the substrate, and the firstsurface is a facet along a crystal plane.
 7. The semiconductor device ofclaim 6, wherein the source/drain region has a second surface connectedto the first surface, and the second surface is a facet along a crystalplane.
 8. The semiconductor device of claim 7, wherein the source/drainregion has the major width on a boundary between the first surface andthe second surface.
 9. The semiconductor device of claim 1, furthercomprising: spacer layers on the sidewalls of the active region toexpose the upper surface and portions of side surfaces of the activeregion.
 10. The semiconductor device of claim 9, wherein thesource/drain region is in contact with the spacer layers and cover anentire sidewall of the active region exposed by the spacer layers. 11.The semiconductor device of claim 1, further comprising: internal spacerlayers on opposite sides of the gate electrode in the first direction onlower surfaces of the plurality of channel layers.
 12. The semiconductordevice of claim 11, wherein the source/drain region has a local minimumwidth further reduced in the second direction in regions having a heightcorresponding to a height of each of the internal spacer layers whencompared to a width in the second direction in regions having a heightcorresponding to a height of each of the plurality of channel layers.13. The semiconductor device of claim 1, further comprising: a contactplug connected to the source/drain region.
 14. The semiconductor deviceof claim 13, wherein the contact plug is recessed in the source/drainregion below a height of an uppermost channel layer, among the pluralityof channel layers.
 15. The semiconductor device of claim 1, wherein theactive region is a structure of an active fin having an upper finsurface and sides running in the first direction.
 16. A semiconductordevice comprising: an active region extending on a substrate in a firstdirection; first and second channel layers sequentially on the activeregion to be vertically spaced apart from each other; a gate electrodeextending in a second direction to intersect the active region on thesubstrate and surrounding the first and second channel layers; and asource/drain region on the active region on at least one side of thegate electrode and disposed to be in contact with the first and secondchannel layers, wherein the source/drain region has a first major widthin the second direction between first protruding points and a secondmajor width in the second direction between second protruding points,the first major width being a largest width of a first region, the firstregion having a height corresponding to a height between an uppersurface of the first channel layer and the active region, the secondmajor width being a largest width in a second region adjacent to thesecond channel layer, the second region having a height corresponding toa height of the second channel layer, and the second major width is lessthan the first major width.
 17. The semiconductor device of claim 16,wherein the source/drain region has a side surface extending from theactive region to the first region having the first major width, and theside surface of the source/drain region is a facet along a crystalplane.
 18. The semiconductor device of claim 16, wherein thesource/drain region has a third width, less than the first major widthand the second major width, between the first region having the firstmajor width and the second region having the second major width.
 19. Asemiconductor device comprising: an active region extending on asubstrate in a first direction having an upper surface and sidewalls; agate electrode extending in a second direction to intersect the activeregion on the substrate; a plurality of channel layers on the activeregion to be vertically spaced apart from each other in a region inwhich the active region and the gate electrode intersect each other;spacer layers on the sidewalls of the active region in the seconddirection and exposing the upper surface and portions of the sidewallsof the active region; and a source/drain region disposed on the activeregion on at least one side of the gate electrode and disposed to be incontact with the plurality of channel layers, wherein the source/drainregion extends from the sidewalls of the active region, exposed by thespacer layers, and inclined with respect to an upper surface of thesubstrate to have a width expanding from both sides of the activeregion, the source/drain region has a major width in the seconddirection between first protruding points in a region adjacent to alowermost channel layer adjacent to the active region among theplurality of channel layers, the major width is in a region having aheight corresponding to a height between the lowermost channel layer andthe active region, and a first distance, in the second direction,between a side surface of the lowermost channel layer and a nearestfirst protruding point is greater than a second distance, in the seconddirection, between a side surface of another of the plurality of channellayers and a nearest second protruding point of the source/drain region.20. The semiconductor device of claim 19, wherein the source/drainregion has a curvature corresponding to a height of the channel layersin a region adjacent to other overlying channel layers.